Posted
by
Unknown Lamer
on Wednesday March 21, 2012 @10:58AM
from the robot-sea-monsters dept.

pigrabbitbear writes with an excerpt from an article at Motherboard: "Earlier last week we heard about the strange blob-bot, an amoeba-mimicking, pulsating, little horror of a robot. But that's nothing in the face of news that engineers at Virginia Tech have built a robotic jellyfish. As if the threat of the oceans being taken over by deadly stinging jelly cyborgs isn't scary enough, there's this: the researchers claim that, because their Robojelly is powered by a hydrogen-based catalytic reaction, rather than electricity, it could 'theoretically' power itself indefinitely. When you consider our best options for powering underwater craft are currently batteries, nuclear reactors, or tethers to the surface, a chemically-powered propulsion system is groundbreaking (and, well, a bit nerve-wracking)."
The full paper is available for free (at least for 30 days; registration required).

Evidently no, now it's just +2 funny, or at least in this case it is, probably because there's no shark involved, so the reference doesn't really work. But I wouldn't really anticipate the reference going away any time soon, considering it is older than Slashdot itself. Same goes for Monty Python, The Simpsons, Star Wars and a shitload of others. Some references are topical, others are timeless. If a reference is still being used after 10 years, it's probably the latter.

RTFA.It uses heat and shape memory alloy to create force. The way shape memory alloy works is that it has one shape when hot and another when cold. The robot has two ways to create this heat; electricity or catalytic action of a platinum catalyst.It is not even clear if the electricity is from a tether or batteries.

The issues with this technology are as follows;1. Currently the only moving version runs on electricity to create the heat.
"A hydrogen-powered version works underwater, but has to be held with a clamp as it isn’t producing enough power to keep itself from sinking."2. The fuel powered version uses hydrogen and oxygen externally supplied and can not even support it's own weight.
"Disappointingly, the authors mention that the Robojelly in the above video is still electrically powered, as the chemical system needs refinement for full power."3. The hydrogen version has no steering capability.
"“We are now researching new ways to deliver the fuel into each segment so that each one can be controlled individually. This should allow the robot to be controlled and moved in different directions.”4. The capability to "gather oxygen and hydrogen its surroundings" has not even been looked into.5. The speed is extremely slow compared with ocean currents. It is little more than a drifter with some depth control.6. It is extremely weak. It's payload capacity is almost zero. It is not all that useful when it can not carry sensors and communication gear.

Specifically, here are the hurdles this technology has to overcome to be viable:1. Shape memory alloy; there is a physical limit to how fast shape memory alloy changes shape. It is not instantaneous. There is a limit to the size of the wire as the heat has to penetrate through the shape alloy wire for full change to occur and then that heat has to be dissipated to change shape back.2. Catalytic heat delivery; How much heat can be delivered in such a cold environment. The system works against itself. It needs cold water to change the shape of the memory alloy wire but not so cold so that the heat generation is overcome. How big a wire can this catalyst power?3. The system to "gather hydrogen and oxygen from its surroundings" has not even been looked into. It may never work as no research has been done on it. At this point is is just an idea. It's like designing a tethered robot and saying "with a fusion motor this robot could run indefinitely".

I love the final sentence from the abstract; "Fuel-powered bell deformation of 13.5% was found to be comparable to that of electrically powered (29%) and natural jellyfish (42%)." The fact that something is comparable does not mean that it compares well. The bell deformation of the fuel-powered version is 32% of that of jellyfish. Is the sufficient to do anything useful?

Yet another premature article about the beginnings of an interesting technology that has yet to overcome a number of huge hurdles. These articles downplay the hurdles to make themselves look more interesting. The researchers have done the easy part but the hard parts may be insurmountable. Considering that the hurdles are so large this technology may never be viable.

The power-itself-indefinitely discovery is way more important than the 'swimming jellyfish' invention. The former would be an astounding change in our understanding of physics...while the latter is mere technology (important but not going to reorder the universe or anything). What the article is claiming is invented here is a method to separate hydrogen gas from the ocean using less energy to accomplish the capture than what they obtain in th